In 2013 I moved to Ndola, a city in northern Zambia, to work on an HIV research project. Ndola is the hub of the country’s copper mining industry, a bustling commercial center that draws entrepreneurs from South Africa and beyond. My organization worked with government clinics in villages around the Ndola area to provide HIV and family-planning counseling, care, and education. I’d recently graduated from a master’s program in public health, and a US-based research organization had hired me to co-lead a year-long study of HIV infection among women.

During the week, my office prepared truckloads of supplies—test kits, condoms, appointment logbooks—and shipped them to the clinics. Once every week, our doctors also treated patients at our headquarters in the city. Ndola, Zambia’s third-largest city, had a great need for affordable, high-quality health care. If at times the cityscape seemed picturesque to me—jacaranda-lined dirt roads, merchants bearing enormous bowls of vegetables upon their heads, uniformed schoolchildren gleefully walking back home at the end of day—there were always reminders of Zambia’s extreme, endemic poverty. For many of the children I saw, home was the sprawling encampments on the city’s outskirts—a maze of rudimentary, one-room structures that housed entire families.

On Wednesdays, dozens of women—teens wearing tank tops and skinny jeans, older women with their waists wrapped in swaths of brightly patterned fabric—would come to our facility. Nearly all of them carried babies on their backs, in their arms, or on their laps. As they waited to see the medical staff, they sat close together on long benches or on the spacious back lawn—talking and laughing, sometimes shaking guavas from the trees in the yard, as familiar with one another as classmates, or even sisters.

The reason that many of them knew each other was because all of them were sex workers. Our study was focused on HIV infection among people from high-risk groups. These women had volunteered to participate in exchange for a small payment, monthly testing, preventive health services, and lunch.

One Wednesday morning, I heard my office door open and turned to see one of our nurses. A statuesque woman with a warm smile, she was known for her compassionate bedside manner. She had news for me. “There has been a seroconversion. Volunteer 739.”

A seroconversion is a change in a patient’s HIV status from negative to positive. Someone had contracted the disease. From a research perspective, this was important news, and my interest was immediately piqued.

I followed the nurse to the counseling area. Before I opened the door to the patient’s room, I paused. Up until this time, I’d had little face time with our visitors—other than exchanging friendly greetings walking to and from the medical lab. To be honest, I had been distracted by all the numbers: the volunteers enrolled, appointment lengths measured, syphilis test kits needed. This was research, and everything was quantifiable.

But now my work was all too personal. The person on the other side of that door had just received devastating news. Suddenly nervous, I stepped inside wearing a smile that I hoped would convey empathy and warmth. I was startled to see that Volunteer 739 was smiling as well. The colorfully dressed young woman—like the other patients, a sex worker—had her slender arms wrapped gently around her body to ward off the chill of the air conditioning. But otherwise she seemed completely at ease—perhaps even happy. Oh no, I thought. She doesn’t know yet.

I left the room. It was better that the nurse, a trained counselor, break the news to the woman privately. I returned to my office with a heavy heart, unable to shake a sense of guilt. It seemed wrong that a stranger from a country on the other side of the world knew such an intimate detail about this woman’s life before she did.

Later, I knocked softly on the same door, my paperwork in hand. The woman’s demeanor had changed dramatically. Now she was crumpled in her seat, head in her hands. I quickly conferred with the nurse and left the room without talking to the young woman: many Zambians live in extremely close quarters, and I knew this might be her last moment alone for a while.

That night, I reviewed Volunteer 739’s file. From her answers to our questions it was clear she had grown up in extreme poverty. She had turned to sex work to survive, and I wondered how much of a choice she’d had along the way. In many other ways, though, she wasn’t so different from me. We were close in age. We both wanted to have kids someday. She was ambitious, too—she’d told us she wanted to get out of sex work and start her own business. How would this diagnosis change all that? How much had changed just in one day?

In research, a boundary exists between scientists and their subjects. There are strict guidelines about what information should and shouldn’t be disclosed. There is a protective distance that prevents one group from getting personally involved with the other. Any information collected is anonymous, stripped of details that could identify the subject. This distance is necessary: it allows researchers to look beyond the individual and tackle large-scale problems. It lends a crucial impartiality to scientific investigations that can improve, and sometimes even save, lives. But equally critical is remembering that these advances in knowledge are built on the contributions of individuals, who have lives just as rich and meaningful and unique as our own. They are more than the “populations” and “cohorts” we analyze, or the variables and trends that appear in our data.

I think of Volunteer 739 sometimes. I have hope for her. I am grateful to her, too. Her moment of deep vulnerability made me rethink my role as a scientist and my relationship with my research subjects. It reminded me of the importance of this person-to-person connection—not just for the individuals we work with, but for researchers, too. They help us as we help them. And there is nothing more human than that.

Jennifer Kotlewski is a writer based in Los Angeles. Her expertise spans health, humanitarian issues, international travel, and the great outdoors. Instagram: @jenkotlewski